Credit: The Associated Press

Officers march into position near the blast site on Boylston Street between Dartmouth and Exeter Streets near the Boston Marathon finish line.

WASHINGTON — The Boston Marathon bombings could provide an opportunity for the U.S. and Russia to find some common ground for cooperation as authorities investigate the two ethnic Chechens accused of carrying out the attack.

Ties between the two nations have soured over disputes about stopping Syria's civil war, child adoptions and other issues. But understanding how the brothers became radicalized is of paramount importance to Washington as it seeks to prevent similar attacks. It's also important to Moscow, which long has battled terrorism in its southern territories.